首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   9732篇
  免费   185篇
  国内免费   1篇
电工技术   57篇
综合类   5篇
化学工业   1053篇
金属工艺   118篇
机械仪表   75篇
建筑科学   218篇
矿业工程   5篇
能源动力   90篇
轻工业   534篇
水利工程   31篇
石油天然气   6篇
武器工业   1篇
无线电   378篇
一般工业技术   918篇
冶金工业   5920篇
原子能技术   58篇
自动化技术   451篇
  2022年   33篇
  2021年   63篇
  2020年   47篇
  2019年   50篇
  2018年   75篇
  2017年   75篇
  2016年   100篇
  2015年   100篇
  2014年   113篇
  2013年   165篇
  2012年   159篇
  2011年   190篇
  2010年   182篇
  2009年   147篇
  2008年   179篇
  2007年   147篇
  2006年   157篇
  2005年   112篇
  2004年   120篇
  2003年   130篇
  2002年   109篇
  2001年   128篇
  2000年   111篇
  1999年   276篇
  1998年   1839篇
  1997年   1107篇
  1996年   731篇
  1995年   420篇
  1994年   343篇
  1993年   395篇
  1992年   103篇
  1991年   112篇
  1990年   123篇
  1989年   127篇
  1988年   96篇
  1987年   112篇
  1986年   103篇
  1985年   98篇
  1984年   40篇
  1983年   50篇
  1982年   62篇
  1981年   58篇
  1980年   77篇
  1979年   46篇
  1978年   46篇
  1977年   170篇
  1976年   281篇
  1975年   44篇
  1974年   29篇
  1970年   28篇
排序方式: 共有9918条查询结果,搜索用时 468 毫秒
1.
2.
3.
The efficient substitution of sucrose by a sweetener in beverages requires the application of some sensory techniques. First, one must determine the concentrations of the sweeteners under study, equivalent in sweetness to the ideal sucrose concentration. In addition, it is fundamental to determine which is most similar to sucrose. The objectives of this study were to determine the ideal sweetness for espresso coffee and the equivalent concentrations in sweetness of different sweeteners, as well as characterise the time–intensity profile of each sweetener in relation to sweetness. The sweeteners evaluated were sucralose, aspartame, neotame, a cyclamate/saccharin mixture (2:1) and stevia. The sucrose concentration considered ideal by consumers was 12.5% (w/v), and the equivalent concentrations of the sweeteners were 0.0159% for sucralose, 0.0549% for aspartame, 0.0016% for neotame, 0.0359% for the cyclamate/saccharin mixture and 0.0998% for stevia. The time–intensity analysis indicated that possibly the sweeteners neotame, aspartame and sucralose would be the best substitutes for sucrose.  相似文献   
4.
Protozoal infections are still a global health problem, threatening the lives of millions of people around the world, mainly in impoverished tropical and sub-tropical regions. Thus, in view of the lack of efficient therapies and increasing resistances against existing drugs, this study describes the antiprotozoal potential of synthetic cinnamate ester analogues and their structure-activity relationships. In general, Leishmania donovani and Trypanosoma brucei were quite susceptible to the compounds in a structure-dependent manner. Detailed analysis revealed a key role of the substitution pattern on the aromatic ring and a marked effect of the side chain on the activity against these two parasites. The high antileishmanial potency and remarkable selectivity of the nitro-aromatic derivatives suggested them as promising candidates for further studies. On the other hand, the high in vitro potency of catechol-type compounds against T. brucei could not be extrapolated to an in vivo mouse model.  相似文献   
5.
6.
The hydrogen content, its depth distribution, and its bonding configuration have been studied in hydrogenated amorphous silicon prepared by plasma-enhanced chemical vapor deposition with hydrogen-diluted silane. Nuclear reaction analysis and infrared spectroscopy were used to determine the total amount of hydrogen and its bonded component, respectively. It has been established that the total concentration of hydrogen does not depend on the film thickness, and has a uniform depth profile. The concentration of bonded hydrogen changes with the film thickness within the measurement accuracy. The data obtained suggest the presence of molecular (non-bonded) hydrogen, uniformly distributed in concentration across the film thickness.  相似文献   
7.
8.
Postgastrectomy syndromes are uncommon but, unfortunately, frustrating for both patient and physician, because treatment with prokinetic agents is often of limited benefit. This article examines the evidence for efficacy of available prokinetic drugs in the management of these difficult disorders.  相似文献   
9.
A device that harnesses the mechanical energy of skeletal muscle contracting in a linear configuration has been implanted in goats. This energy convertor transforms muscle work to hydraulic energy that could drive a variety of cardiac assist devices. The device is mounted with a rib clamp and plate affixed to the sternum by cortical bone screws. A transcutaneous hydraulic line carries a silicon based working fluid to an external system that controls the muscle load. In 60 to 70 kg goats, the latissimus dorsi insertion was reattached to the energy convertor. A Telectronics myostimulator with intramuscular electrodes stimulated the latissimus dorsi. In acute implants, hydraulic pressures in excess of 150 psi were obtained. Chronic implantation of the device allowed system evaluation in the conscious unanesthetized animal. Two weeks after implant, hydraulic pressures in excess of 200 psi were obtained and energy transferred to the external loading system exceeded 1 J per contraction. Six weeks after implant, the device continued to cycle freely. These initial results are very promising and suggest an implantable energy convertor is feasible. Development of an energy convertor is an important step toward tether-free skeletal muscle powered cardiac assist devices.  相似文献   
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号